A Wide Area Network (WAN) is a computer network that covers a broad area, e.g., a network whose communications links cross metropolitan, regional, or national boundaries. This is in contrast to personal area networks (PANs), local area networks (LANs), campus area networks (CANs), or metropolitan area networks (MANs) which are usually limited to a room, building, campus or specific metropolitan area (e.g., a city), respectively.
WANs are often used to connect LANs and other types of networks together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization's LAN to the Internet. WANs are often built using leased lines. At each end of the leased line, a router connects to the LAN on one side and to a hub within the WAN on the other. WANs can also be built using less costly circuit switching or packet switching methods. Network protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) can provide transport and addressing functions within WANs.